Valve

ABSTRACT

A valve comprises an orifice plate ( 1 ) having one or more orifices ( 4 ) through which a fluid may flow, and one or more piezo-electric elements ( 2 ). Each element ( 2 ) has a face positioned to contact the orifice plate at an orifice. Each element has a first state in which it abuts the plate to prevent flow of fluid through the associated orifice and a second state in which the face is spaced from the plate to allow flow through the associated orifice. A controller ( 50 ) selectively applies a first voltage to an elements to cause it to adopt the first state and applies a second voltage to the one or more elements to cause the elements to adopt the second state.

BACKGROUND

Some applications of valves require a valve which is small and operableat high frequency. One example, amongst others, of such an applicationis an air valve array for a fluid dispenser for example an ink jetprinter.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features and advantages of the present disclosure will beapparent from the detailed description which follows, taken inconjunction with the accompanying drawings, which together illustrate,by way of example only, features of the present disclosure, and wherein:

FIG. 1A is a schematic diagram of an example of a valve;

FIG. 1B is a schematic end view of an orifice plate of the valve of FIG.1A;

FIG. 2A is a schematic cross sectional view of the valve of FIG. 1 withthe valve closed and FIG. 2B is a partial view showing the valve open;

FIG. 3A is a schematic view of a fluid dispenser including the valve ofFIG. 2 open and FIG. 3B shows the fluid dispenser with the valve closed;

FIGS. 4A and 4B are schematic diagrams showing relative positions of theorifice plate and fluid drops;

FIG. 5 is a graph showing the relationship of droplet deflection andrelative position of the orifice plate and fluid drops;

FIG. 6 is a graph showing the variation of the width of an air jet withdistance from the orifice plate;

FIG. 7 is a schematic diagram showing air jets produced by the orificeplate;

FIG. 8 is a graph showing the variation of droplet displacement withdistance from the orifice plate; and

FIG. 9 is a schematic diagram of a fluid dispensing apparatus.

DETAILED DESCRIPTION

Referring to FIG. 1A, the valve comprises an orifice plate 1 and aplurality of elongate piezoelectric elements 2 supported by a support 6.The orifice plate 1 defines a plurality of orifices 4, one for eachpiezo-electric element 2, through which a fluid may flow. In examplesdescribed below the fluid is gas. Each piezo-electric element 2 haselectrodes (not shown) arranged in known manner relative to the polarityof the element to cause the length of the element 2 to change linearlyin a direction perpendicular to the orifice plate 1 when a voltage isapplied to the electrodes. In one state, an element 2 abuts the orificeplate 1 and blocks the orifice (indicated by 4A for example) associatedwith it and in another state the element is spaced from the orificeplate 1 and thus the associated orifice (indicated by 4B for example) isnot blocked.

As will be described hereinbelow, such a valve may have very smalldimensions; for example there may be ten to twenty or more piezoelectricelements per mm. The valve can operate at high frequency; some examplesoperate at 250 kHz. A piezo-electric element of PMN-PT (Lead MagnesiumNiobate-Lead Titanate) may change in length by 4 micrometers in 4microseconds with an applied voltage of 60V. Whilst the example of FIG.1 has a plurality of piezo-electric elements and orifices, it will beappreciated that a valve could have only one element and one orifice.Furthermore, whilst the example of FIG. 1 shows for simplicity onlyseven piezo-electric elements 2 and orifices 1, the valve may have anyother number of elements and orifices. For example the valve may havehundreds of elements and orifices. Examples of the valves may have 10 to20 orifices per mm. The orifices may have a diameter of 10 to 50micrometers. In an example the orifices have a diameter of 40micrometers. The width W of each piezo-electric element may be 40 to 80micrometers.

Referring to FIGS. 2A and 2B, an example of the valve comprises a closedchamber 10 defined by a support 6, the orifice plate 1, a hood 8, an endwall 16 opposite the orifice plate, and lateral end walls (not shown)which extend between the orifice plate and the end wall. The orificeplate 1, hood 8 and support 6 may be of any suitable stiff material forexample silicon, stainless steel, beryllium copper, or other metals. Inan example of the valve, the orifice plate is of silicon. The support 6supports at least one, in this example a plurality of, piezo-electricelements 2 within the chamber 10. Each element 2 is fixed to the supportat one end remote from the orifice plate 1, the remainder of the elementbeing free to move, sliding on the support 6, to block and unblock anorifice in the plate 1. In the example of FIGS. 2A and 2B, thepiezo-electric element is fixed to the support by adhesive. The chamberhas an inlet port 14 in this example for supplying pressurized gas, inthis example air, from a source (not shown) to the chamber 10. Anactuating voltage is applied to each element 2 by an actuator 50 coupledto the electrodes of the piezo-electric element 2 by conductors 54. In afirst state of the actuating voltage the piezo-electric element 2 abutsthe orifice plate 1 and blocks its associated orifice as shown in FIG.2A. In a second state of the actuating voltage the piezo-electricelement 2 is spaced from the orifice plate 1 and the pressurized airexits the chamber through the orifice as an air jet as shown in FIG. 2B.

The actuator 50 may be responsive to control signals 52 from a controldevice for example a computer which controls the operation of the valve.

Referring to FIGS. 3A and 3B, the valve may be used in a fluid ejectionsystem which in this example is an ink jet printer. FIGS. 3A and 3Bschematically show, for simplicity, one section, associated with onepiezoelectric element 2 and one orifice 4, of a print head 40. The printhead comprises one or more valves.

The section of the print head 40 shown in FIGS. 3A and 3B comprises asource 56 of ink which supplies ink under pressure to a nozzle 60. Thesource 56 and nozzle 60 are vibrated by a vibrator 58 which may be apiezoelectric vibrator to create ink drops 62 which are jetted towards aprint medium 36. The ink drops are jetted along a drop path past thevalve before they reach the print medium 36. When the orifice 4 is notblocked as shown in FIG. 3A, an air jet 48 diverts one or more dropsinto a gutter 66 for recirculation back to an ink reservoir (38 in FIG.9) via a suction tube 68. When the orifice is blocked as shown in FIG.3B, the drops are not diverted and reach the print medium. The printmedium and the print head move one relative to the other and drops areallowed to reach the print medium or be diverted to the gutter under thecontrol of a data source to print desired indicia on the medium 36 aswill be described with reference to FIG. 9.

Referring to FIGS. 4A and 4B, an example of the print head 40 (see FIG.3A) has a plurality of nozzles 60 and a like plurality of orifices 4 andpiezo-electric elements 2. In an example, each nozzle is arranged toproduce drops of fluid having a volume of about 14 picolitres at a rateof 135 KHz. The orifices in the orifice plate have a diameter of about18 micrometers and are spaced by 338/2=169 micrometers. Air is suppliedto the chamber 10 (see FIG. 3A) at a pressure of about 0.45 barproducing air jets when the orifices 4 are open of about 1.5 bar. FIG.4A shows the air jets 48 aligned with the drops and FIG. 4B shows theair jets 48 offset in the X direction, the direction of the path of thedrops, from the drops by 338 micrometers. The orifice plate is spacedfrom the drop path by the spacing Y.

FIG. 5 is an example graph showing the variation in angle of dropdeflection with direction X for two values of Y, 0.2 mm and 0.4 mm. FIG.7 is an example graph showing the width of an air jet with distance fromthe orifice plate. FIG. 6 shows, consistently with FIG. 5, a workingrange of value Y of 0.1 mm to 0.2 mm. FIG. 7 shows that at 0.2 mm formthe orifice plate the air jets 48 do not overlap minimizing cross talkbetween adjacent orifices. FIG. 8 is an example graph showing thevariation with orifice to drop distance Y of drop deflection at 1 mmfrom the drop plate. It shows that over the working range of Y=0.1 to0.2 mm the deflection varies approximately linearly.

In one example, the number of orifices and of piezoelectric elements ina valve is selectable by the designer. An array of a plurality of valveseach comprising one or more orifices and piezoelectric elements may beused in one print head.

The dimensions and spacing of the orifices and of the piezoelectricelements is selectable by the designer. In practice, the dimensions andspacing may be limited by the chosen method of making the piezo-electricelements. In one example the elements are made by mechanically cutting apiezo-electric crystal which provides a minimum spacing between adjacentelements of about 10 micrometers. Referring to FIGS. 1 and 2,illustrative dimensions for a piezo-electric element are 5 mm long (Lperpendicular to the orifice plate 1), 0.1 mm thick (D) and 0.08 mm wide(W parallel to the orifice plate) for an orifice 4 of diameter less than0.08 mm. Such dimensions are suitable for printing at a resolution ofabout 250 dots per inch (dpi) using 10 piezo-electric elements andorifices per mm. With other methods of making the elements, smallerdimensions may be achieved.

FIG. 9 schematically shows an example of an inkjet printing system 20using the valve described herein above. The inkjet printing system 20constitutes one example of a fluid ejection system that includes a fluidejection device, such as inkjet print head assembly 22, and a fluidsupply assembly, such as ink supply assembly 24. The inkjet printingsystem 20 also includes a mounting assembly 26, a media transportassembly 28, and an electronic controller 30. At least one power supply32 provides power to the various electrical components of inkjetprinting system 20.

In one example, inkjet print head assembly 22 includes one or more printheads 40 as described above that eject drops of ink through a pluralityof nozzles 60 toward a print medium 36 so as to print onto print medium36.

Print medium 36 may be any type of suitable sheet material, such aspaper, card stock, transparencies, Mylar, fabric, and the like.

Typically, nozzles 60 are arranged in one or more columns or arrays suchthat properly sequenced ejection of ink from nozzles 60 causescharacters, symbols, and/or other graphics or images to be printed uponprint medium 36 as inkjet print head assembly 22 and print medium 36 aremoved relative to each other. While the following description refers tothe ejection of ink from print head assembly 22, it is understood thatother liquids, fluids or flowable materials, including clear fluid, maybe ejected from print head assembly 22.

Ink supply assembly 24 as one example of a fluid supply assembly 30provides ink to print head assembly 22 and includes a reservoir 38 forstoring ink. As such, ink flows from reservoir 38 to inkjet print headassembly 22. Ink supply assembly 24 and inkjet print head assembly 22form a recirculating ink delivery system as described above. In arecirculating ink delivery system as shown in FIGS. 3A and 3B, only aportion of the ink provided to print head assembly 22 is consumed duringprinting. Ink not consumed during printing is returned to ink supplyassembly 24.

In one example, inkjet print head assembly 22 and ink supply assembly 24are housed together in an inkjet cartridge or pen. The inkjet cartridgeor pen is one example of a fluid ejection device. In another example,ink supply assembly 24 is separate from inkjet print head assembly 22and provides ink to inkjet print head assembly 22 through an interfaceconnection, such as a supply tube (not shown). In either example,reservoir 38 of ink supply assembly 24 may be removed, replaced, and/orrefilled. In one example, where inkjet print head assembly 22 and inksupply assembly 24 15 are housed together in an inkjet cartridge,reservoir 38 includes a local reservoir located within the cartridge andmay also include a larger reservoir located separately from thecartridge. As such, the separate, larger reservoir serves to refill thelocal reservoir, for example source 56 of FIG. 3. Accordingly, theseparate, larger reservoir and/or the local reservoir may be removed,replaced, and/or refilled.

Mounting assembly 26 positions inkjet print head assembly 22 relative tomedia transport assembly 28 and media transport assembly 28 positionsprint medium 36 relative to inkjet print head assembly 22. Thus, a printzone 37 is defined adjacent to nozzles 60 in an area between inkjetprint head assembly 22 and print medium 36.

In one example, inkjet print head assembly 22 is a scanning type printhead assembly. As such, mounting assembly 26 includes a carriage (notshown) for moving inkjet print head assembly 22 relative to mediatransport assembly 28 to scan print medium 36. The assembly 26 comprisesfor example a print head 40 having a plurality of orifices 4 andpiezo-electric elements 2 extending in the direction of movement of theprint medium. The carriage scans the print head 40 across the printmedium to simultaneously print a plurality of lines across the medium.

In another example, inkjet print head assembly 22 is a non-scanning typeprint head assembly. As such, mounting assembly 26 fixes inkjet printhead assembly 22 at a prescribed position relative to media transportassembly 28. Thus, media transport assembly 28 positions print medium 36relative to inkjet print head assembly 22. The assembly comprises afixed array of print heads extending perpendicular to the direction ofmovement of the print medium. Each print head comprises a plurality ofdrop sources, orifices 4 and piezo-electric elements 2 arranged tosimultaneously print on the print medium 36.

Electronic controller or printer controller 30 typically includes aprocessor, firmware, and other electronics, or any combination thereof,for communicating with and controlling inkjet print head assembly 22,mounting assembly 26, and media transport assembly 28. Electroniccontroller 30 receives data 39 from a host system, such as a computer,and usually includes memory for temporarily storing data 39. Typically,data 39 is sent to inkjet printing system 20 along an electronic,infrared, optical, or other information transfer path. Data 39represents, for example, a document and/or file to be printed. As such,data 39 forms a print job for inkjet printing system 20 and includes oneor more print job 10 commands and/or command parameters.

In one example, the controller 30 sends control data 52 to the actuatingdevice 50 shown in FIG. 2A to actuate the valve and to control whichdrops 62 reach the print medium 36. As such, electronic controller 30defines a pattern of ejected ink drops that form characters, symbols,and/or other graphics or images on print medium 36. The pattern of 15ejected ink drops is determined by the print job commands and/or commandparameters.

The piezo-electric elements of the examples described above are ofPMN-PT but other examples could use other piezo-electric materials forexample PZT (Lead Zirconium Titanate). PMN-PT allows higher frequencyoperation and allows smaller dimensions to be achieved than othermaterials currently available. The piezo electric elements describedabove have a rectangular cross section, but could have othercross-sectional shapes. The piezoelectric elements described abovechange length linearly to block and unblock the orifices 4. In otherexamples, the elements may bend to block and unblock the orifices butsuch a mode of operation is slower that changing length linearly.

The valve of FIGS. 1 and 2 may be used for purposes other than in afluid ejection system as described with reference to FIGS. 3 to 9.

What is claimed is:
 1. A printer comprising: a fluid source comprising anozzle to eject drops from the fluid source; a gas jet along a path ofdrops ejected from the nozzle; a valve comprising a piezo electricdevice to block and unblock the gas jet; a controller to selectivelyoperate the valve to deflect some drops ejected from the nozzle out ofthe path with the gas jet and to allow other drops ejected from thenozzle to follow the path to a print medium, wherein drops areselectively deflected or allowed to reach the print medium in accordancewith data from a host device defining an image to be printed; whereinthe gas jet comprises an inlet port to receive pressurized gas, theinlet port being out of line with an orifice to release a stream of gas,the piezo electric device being in-line with the orifice and not theinlet port.
 2. The printer of claim 1, wherein: the gas jet comprises anorifice plate, the orifice being formed in the orifice plate anddirecting a flow of gas under pressure into the path of drops; and thepiezo electric device of the valve moves linearly in a directionperpendicular to the orifice plate to selectively block or unblock theorifice to the flow of gas.
 3. The printer of claim 1, furthercomprising a gutter to collect drops deflected from the path by the gasjet.
 4. The printer of claim 3, further comprising a recirculatingsystem to return drops from the gutter to the fluid source.
 5. Theprinter of claim 1, further comprising a vibrator to eject drops fromthe fluid source via the nozzle.
 6. The printer of claim 1, wherein: thefluid source comprises an array of nozzles; the gas jet comprises anorifice plate with an array of orifices, each orifice to direct a gasjet into a path of drops from a corresponding nozzle of the nozzlearray, each orifice being controlled by a valve with a piezo electricdevice; and the controller to independently operate the piezo electricdevice in each of the valves for all of the gas jets in accordance withthe data from a host device defining an image to be printed.
 7. Theprinter of claim 6, wherein there are 10 to 20 orifices per millimeterin the orifice plate.
 8. The printer of claim 6, wherein the orificeshave a diameter in the range 10 to 50 micrometers.
 9. The printer ofclaim 6, wherein the piezoelectric devices each have a width at theorifice plate in the range 40 to 80 micrometers.
 10. The printer ofclaim 1, wherein the piezo-electric device comprises Lead MagnesiumNiobate-Lead Titanate.
 11. The printer of claim 1, further comprising amedia transport assembly for moving a print medium through a print zonedefined by the path of the drops ejected from the nozzle.
 12. A systemfor selectively dispensing a liquid, the system comprising: a liquidsource comprising a nozzle to eject drops from the liquid source; a gasjet along a path of drops ejected from the nozzle, the gas jetcomprising an orifice in an orifice plate to emit a stream ofpressurized gas into the path of drops ejected from the nozzle; a valvecomprising a piezo electric device to expand and retract longitudinallyto block and unblock the orifice of the gas jet, where the piezoelectric device of the valve moves linearly in a direction perpendicularto the orifice plate to selectively block or unblock the orifice to theflow of gas; a controller to selectively operate the valve to deflectsome drops ejected from the nozzle out of the path with the gas jet andto allow other drops ejected from the nozzle to follow the path to atarget zone, wherein drops are selectively deflected or allowed to reachthe target zone in accordance with data from a host device.
 13. Thesystem of claim 12, further comprising a gutter to collect dropsdeflected from the path by the gas jet.
 14. The system of claim 13,further comprising a recirculating system to return drops from thegutter to the liquid source.
 15. The system of claim 12, furthercomprising a vibrator to eject drops from the liquid source via thenozzle.
 16. The system of claim 12, wherein the gas jet comprises aninlet port to receive pressurized gas, the inlet port being out of linewith the orifice, the piezo electric device being in-line with theorifice and not the inlet port.
 17. A method for selectively dispensinga liquid, the method comprising: ejecting drops from nozzles of a liquidsource that comprises an array of nozzles; with a gas jet comprising anorifice plate with an array of orifices, each orifice being along a pathof drops ejected from the array of nozzles, selectively emitting astream of pressurized gas from an orifice of the gas jet into acorresponding path of drops ejected from the array of nozzles to deflecta drop out of a trajectory to a target zone of a print medium; with acontroller, selectively applying a voltage to a piezo electric device ofa valve of each orifice of the gas jet to expand and retract the piezoelectric device longitudinally to block and unblock the correspondingorifice of the gas jet to deflect some drops ejected from the array ofnozzles out of the path with the gas jet and to allow other dropsejected from the array of nozzles the path to the target zone, whereindrops are selectively deflected or allowed to reach the target zone inaccordance with data from a host device.
 18. The method of claim 17,further comprising collecting drops deflected from the path by the gasjet with a gutter.
 19. The method of claim 18, further comprisingrecirculating drops from the gutter to the liquid source.
 20. The methodof claim 17, further comprising moving the array of nozzles relative tothe array of orifices between positions providing maximum and minimumdeflection of the drops.